Then you need to set the 'IsLoading' variable to true just before you call the long running code such as a logging request that waits on a web server to respond. When the code has been executed, set 'IsLoading' back to false. Note: the function that executes this, needs to be asynchronous.

Then it's just a case on wrapping your xaml page in an 'AbsoluteLayout' and adding the below as the last thing before closing the 'AbsoluteLayout':